HOW RELIABLE IS THE LIPPINCOTT-SCHROEDER POTENTIAL FOR THE OH-CENTER-DOT-CENTER-DOT-N HYDROGEN-BONDED FRAGMENT IN THE GAS-PHASE

Ab initio calculations at the MP2 level of theory, with a 6-31 G basis set which includes polarization functions on the atoms involved in th e H bond, are performed on the hydrogen-bonded phenol-NH3 complex. The equilibrium O...N distance (R(e)) is equal to 2.837 Angstrom. The pot ential profile along the proton coordinate at a fixed O...N distance V (r, R(e)) has only one minimum. Its shape is verified by calculation o f the OH stretch frequency. The Lippincott-Schroeder potential is able to reproduce the shape of the V(r, R(e)) function for systems with an O-H...N fragment in the gas phase only if some its parameters are cal ibrated to fit high-level ab initio data.